Revisiting ChicxulubNews story originally written on March 4, 2010

We know that more than half of the plant and animal species on Earth died out then, but we don't know what caused the extinction. Now, a team of 41 scientists from 12 nations has prepared a paper that suggests that the K-Pg extinction was caused by a single impact near what is now Chicxulub, Mexico.

In their paper, the scientists point out that when the asteroid hit the Earth near Chicxulub, it exploded and threw huge amounts of dust and asteroid material into the air. When all of that material settled back to Earth, it formed a clay layer that can still be seen in rocks around the world. Within the layer, scientists have found high levels of iridium. This heavy element is not normally found in high concentrations at Earth's surface, but it is found in asteroids and comets.

The impact between the asteroid and the Earth created a crater that is more than 180 kilometers in diameter. It also caused tsunami, earthquakes and fires; extended (but not total) darkness; cooling temperatures and acid rain. It would have also changed the Earth's climate.

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